Damian Thompson is Editor of Telegraph Blogs and a columnist for the Daily Telegraph. He was once described by The Church Times as a "blood-crazed ferret". He is on Twitter as HolySmoke. His latest book is The Fix: How addiction is taking over your world. He also writes about classical music for The Spectator.

Gay clergy should follow their conscience and defy the Church of England’s restrictions on same-sex marriage, a prominent bishop has said as the most radical change ever made to the legal definition of marriage in Britain comes into force.

The Rt Rev Alan Wilson, the Bishop of Buckingham, said priests should be “creative” to get around restrictions on blessings for same-sex couples and that gay clergy who wish to marry should do so in defiance of the official line.

He also claimed that several current serving bishops are themselves in gay partnerships, and urged them to publicly acknowledge their status for the sake of “honesty and truthfulness” and even consider marrying.

Joined by an alliance of seven retired bishops, he condemned the Church’s position on gay marriage as “morally outrageous” and said it made him “ashamed”.

Bishop Wilson is a suffragan, not in charge of a diocese – but, really, that doesn't matter. He's a serving bishop with, it would appear, a ruthless streak: not so long ago, it was only Peter Tatchell who would state publicly that C of E bishops were in gay partnerships and should out themselves. And if they choose not to? Bishop Wilson won't do it for them, but he must know that others will.

The Church's real problem, however, is not the hypocrisy of closeted prelates. It's that so many priests are perfectly content to solemnise homosexual marriages in church and will indeed be "creative" in finding ways to do so.

How will Archbishop Justin Welby respond? "I think the church has reacted by fully accepting that it's the law, and should react on Saturday by continuing to demonstrate in word and action, the love of Christ for every human being," he told the Guardian in best Rev J C Flannel mode. Uh-huh. Oh, and there will be "structured conversations" to help resolve the problem.

Here's my prediction. As of today, pro-gay clergy will begin to unpick Cameron's "triple lock" banning parishes from holding gay weddings; during the next Parliament it will cease to exist. Priests who want to marry same-sex couples, or indeed marry their own gay lovers, will just do it. Anglo-Catholic and Evangelical parishes that reject the whole notion won't be forced to host such ceremonies, but both these wings of the C of E are moving in a liberal direction, and in the long run demographic change will finish the job.

It's hard to overestimate the weakening effect this will have on the central structures of the Church. The General Synod's deliberations will be rendered irrelevant. The fiction of the "Anglican Communion" will be abandoned. Conservative provinces in Africa will repudiate the C of E; the last Lambeth Conference's disciplinary action against the anything-goes American Episcopal Church will cease to mean anything.

In the 1990s, when I started reporting on Anglican affairs, gay marriage was regarded as a non-negotiable horror by most clergy and churchgoers. The shattering of that consensus has happened far more quickly than even the most optimistic Christian gay campaigners thought possible.

And if the centre cannot hold, one has to ask: what is up for negotiation next? Belief in an afterlife? The divinity of Jesus of Nazareth? After today, one thing is uncomfortably clear: the Church of England has lost the power – and even the inclination – to draw a line in the sand.